Electromagnetic (EM) medical technologies are rapidly expanding worldwide for both diagnostics and therapeutics. As these technologies are low-cost and minimally invasive, they have been the focus of significant research efforts in recent years. Such technologies are often based on the assumption that there is a contrast in the dielectric properties of different tissue types or that the properties of particular tissues fall within a defined range. Thus, accurate knowledge of the dielectric properties of biological tissues is fundamental to EM medical technologies. Over the past decades, numerous studies were conducted to expand the dielectric repository of biological tissues. However, dielectric data is not yet available for every tissue type and at every temperature and frequency. For this reason, dielectric measurements may be performed by researchers who are not specialists in the acquisition of tissue dielectric properties. To this end, this paper reviews the tissue dielectric measurement process performed with an open-ended coaxial probe. Given the high number of factors, including equipment- and tissue-related confounders, that can increase the measurement uncertainty or introduce errors into the tissue dielectric data, this work discusses each step of the coaxial probe measurement procedure, highlighting common practices, challenges, and techniques for controlling and compensating for confounders.

Background. The aim of this study was to analyze the effect of vestibular schwannoma microsurgery via the retrosigmoid-transmeatal approach with special reference to the postoperative tinnitus outcome. Material and Methods. A prospective study was performed in 89 consecutive patients with unilateral vestibular schwannoma indicated for microsurgery. Patient and tumor related parameters, pre- and postoperative hearing level, intraoperative findings, and hearing and tinnitus handicap inventory scores were analyzed. Results. Cochlear nerve integrity was achieved in 44% corresponding to preservation of preoperatively serviceable hearing in 47% and useful hearing in 21%. Main prognostic factors of hearing preservation were grade/size of tumor, preoperative hearing level, intraoperative neuromonitoring, tumor consistency, and adhesion to neurovascular structures. Microsurgery led to elimination of tinnitus in 66% but also new-onset of the symptom in 14% of cases. Preservation of useful hearing and neurectomy of the eighth cranial nerve were main prognostic factors of tinnitus elimination. Preservation of cochlear nerve but loss of preoperative hearing emerged as the main factor for tinnitus persistence and new onset tinnitus. Decrease of THI scores was observed postoperatively. Conclusions. Our results underscore the importance of proper pre- and intraoperative decision making about attempt at hearing preservation versus potential for tinnitus elimination/risk of new onset of tinnitus.

In this work, a prototype of a laboratory microwave imaging system suitable to methodically test the ability to image, detect, and classify human brain strokes using microwave technology is presented. It consists of an antenna array holder equipped with ten newly developed slot bowtie antennas, a 2.5 D reconfigurable and replaceable human head phantom, stroke phantoms, and related measuring technology and software. This prototype was designed to allow measurement of a complete S-matrix of the antenna array. The reconfigurable and replaceable phantom has currently 23 different predefined positions for stroke phantom placement. This setting allows repeated measurements for the stroke phantoms of different types, sizes/shapes, and at different positions. It is therefore suitable for large-scale measurements with high variability of measured data for stroke detection and classification based on machine learning methods. In order to verify the functionality of the measuring system, S-parameters were measured for a hemorrhagic phantom sequentially placed on 23 different positions and distributions of dielectric parameters were reconstructed using the Gauss-Newton iterative reconstruction algorithm. The results correlate well with the actual position of the stroke phantom and its type.

Abstract-Objective:In this paper we present a study of a novel method to noninvasively monitor temperature during thermotherapy for instance in cancer treatment using M-sequence radar technology. The main objective is to investigate the temperature dependence of reflectivity in UWB radar signal in gelatine phantoms using electrically small antennas. Methods: The phantom was locally heated up, and consequently changes of signal reflectivity were observed. Results: An approximate linear relationship between temperature change and reflectivity variations was formulated. To show the potential of this approach we used an M-sequence MIMO radar system. The system was tested on breast-shape phantom with local heating by circulating water of controlled temperature. Delay and Sum algorithm was implemented for two-dimensional imaging. Significance: The article is a study of temperature measurement using UWB radar system for possible usage in thermotherapy.

The real‐time detection of brain strokes is addressed within the Learning‐by‐Examples (LBE) framework. Starting from scattering measurements at microwave regime, a support vector machine (SVM) is exploited to build a robust decision function able to infer in real‐time whether a stroke is present or not in the patient head. The proposed approach is validated in a laboratory‐controlled environment by considering experimental measurements for both training and testing SVM phases. The obtained results prove that a very high detection accuracy can be yielded even though using a limited amount of training data.